1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly, to a method for manufacturing a vertically structured light emitting diode (LED) capable of easily performing a chip separation process for individual elements.
2. Description of the Related Art
A gallium nitride (GaN)-based semiconductor, which is represented as AlxGayIn1−x−yN (0≦x≦1, 0≦y≦1, 0≦x+y≦1), is a compound semiconductor material adaptive for light-emitting in ultraviolet region, and is used for a blue or green light emitting diode (LED). The GaN-based LED that is being used up to date is mainly classified into two types, of which one is a horizontally structured GaN-based LED and the other is a vertically structured GaN-based LED. In the horizontally structured GaN-based LED, both a p-electrode and an n-electrode are disposed at the same side of the device. Accordingly, the total area of the LED device should be great for securing a sufficient light-emitting area. In addition, since a transparent electrode and the n-electrode are close to each other, the horizontally structured GaN-based LED is vulnerable to electrostatic discharge (ESD).
On the contrary, the vertically structured GaN-based LED has several advantageous merits in comparison with the horizontally structured GaN-based LED. In the vertically structured GaN-based LED, the p-electrode and the n-electrode are disposed opposite to each other, wherein a GaN-based epitaxial layer is interposed therebetween.
Typically, the vertically structured GaN-based LED is manufactured through an attachment process of a conductive substrate (e.g., a silicon or a gallium arsenide (GaAs) substrate) and a removal process of a growth substrate (e.g., a sapphire substrate). Korean Patent Laid-Open Publication No. 2004-58479 discloses a method for manufacturing a vertically structured GaN-based LED including an attachment process of a Si substrate, a removal process of a sapphire substrate, and a dicing process of the Si substrate.
FIGS. 1A through 1F are cross-sectional views illustrating a conventional method for manufacturing a vertically structured GaN-based LED. To begin with, referring to FIG. 1A, an n-type clad layer 15a, an active layer 15b and a p-type clad layer 15c, which are formed of a GaN-based semiconductor, are sequentially formed on a sapphire substrate 11, to thereby form a light-emitting structure 15. Thereafter, referring to FIG. 1B, a trench 20 is formed so as to divide the light-emitting structures 15 into individual device regions, and a p-electrode 16 is then formed on the p-type clad layer 15c. Afterwards, referring to FIG. 1C, a conductive substrate 21 such as a Si substrate, a GaAs substrate, or the like is attached on the p-electrode 16 using a conductive adhesive layer 17 such as gold (Au) or the like. Subsequently, the sapphire substrate 11 is removed from the light-emitting structure 15 by means of laser lift-off process. In detail, a laser beam 18 is irradiated on the sapphire substrate 11 so that the sapphire substrate 11 is removed from the light-emitting structure 15. Accordingly, there is obtained the resultant structure where the sapphire substrate 11 is removed, as illustrated in FIG. 1D. Thereafter, referring to FIG. 1E, an n-electrode 19 is formed on the n-type clad layer 15a. Next, referring to FIG. 1F, the resultant structure of FIG. 1E is divided into individual elements through chip separation process, thereby obtaining a plurality of vertically structured GaN-based LEDs 10 simultaneously.
According to the conventional method, the process of cutting away the conductive substrate 21 should be performed for separating the chips from one another. In order to cut away the conductive substrate 21, a dicing process of cutting the conductive substrate 21 should be performed with a cutting wheel. Otherwise, a complicated process such as scribing and breaking process should be performed. Therefore, the manufacturing cost is increased and the total process time is delayed resultingly, due to this complicated process. In addition, in case of using the Si substrate or the GaAs substrate as the conductive substrate 21, the efficiency of heat release is poor and further the device characteristic is deteriorated when high current is applied thereto, because the thermal conductivity of the substrate 21 is not so good. Moreover, while attaching the conductive substrate on the light-emitting structure 15, a crack may occur in the light-emitting structure 15 so that the device may be damaged in the end. This problem may also occur in the manufacturing process of vertically structured LEDs using other compound semiconductors of group III-V, e.g., vertically structured AlGaInP-based LED, AlGaAs-based LED, or the like.